Decahydroacenaphthene process and use



nited States Patent U.S. Cl. 260-666 8 Claims ABSTRACT OF THE DISCLOSURE Decahydroacenaphthene, an improved high energy jet fuel, is formed by reacting cyclododecatriene with an acid catalyst at temperatures in the range of from 50 to 250 C. In addition to decahydroacenaphthene, octahydroacenaphthene and acenaphthene are recovered as by-products of the reaction. These by-products are easily hydrogenated to decahydroacenaphthene in high yields.

The present invention relates to improved jet fuels and to processes for their preparation. More particularly, this invention relates to a jet fuel having high energy per unit volume, low freezing point and high thermal stability, viz, a decahydroacenaphthene comprising fuel. Yet more particularly this invention relates to economic processes for the preparation of such a jet fuel. Most particularly, this invention relates to an improved simple process for the preparation of decahydroacenaphthene and/or acenaphthene from cyclododecatriene.

One of the outstanding problems connected with the development of supersonic aircraft is the dissipation of heat from the jet engine. At subsonic speeds heat can be dissipated to the atmosphere by air-cooling the engine. However, at supersonic speeds, the heat builds up faster than the air can absorb it and therefore other methods for cooling must be used. A preferred method is to utilize the fuel as a heat exchange reservoir to cool the lubricating and/or hydraulic oils before they are recycled to the engine and/or the refrigerant used to cool the cockpit and instruments before it is recycled. In the utilization of conventional petroleum distillate feeds the fuel temperature builds up to such an extent that harmful deposits are formed in the precombustion phase of the fuel system. Thus, these fuel temperatures cause deposits to be formed which interfere with normal fuel composition as well as temperature control. This thermal stability problem is so serious that it can eventually lead to engine failure of the turbine section due to uneven temperature patterns. It has been found that conventional gasoline anti-oxidants are incapable of overcoming this impressive problem. In addition, in these supersonic jet aircraft the power developed is directly proportional to the heat of combustion energy per unit volume of the fuel, and therefore a fuel having a high energy per unit volume is also necessary.

It has now been discovered that the present jet fuel is highly superior in all these respects to most other synthetic fuels presently known. In addition an extremely economic process has now been developed to supply this fuel from cheaply available raw materials. Recently, it was discovered that butadiene can be trimerized to 1,5,9-

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cyclododecatriene in the presence of a metallic organo catalyst such as a titanium organo catalyst. A process for preparing this cyclododecatriene is described for example in Angewandte Chemie, vol. 69 column 11:397 (June '7, 1957). According to this process extremely high conversions and selectivities are obtained to the desired products.

It should be noted that although four stereo isomers of 1,5,9-cyclododecatriene are theoretically possible only two are ordinarily obtained. These are the cis, trans, trans (cis, tr., tr.) and the trans, trans, trans (tr., tr., tr.) as shown by the formulas below.

Although recent data indicate that there is some question whether the cis, trans, trans isomer is in fact a cis, cis, trans isomer this does not affect the teaching of this invention since the proper melting point for the isomer is above identified. Throughout in the specification it will be assumed that either of the isomers above represented or of the other isomers may be utilized or mixtures thereof, since the desired material may be prepared from all of these.

According to the present invention it has now been discovered that cyclododecatriene, either pure or as a crude mixture with other reaction products from the trimerization step (after separation of catalyst), may be reacted with an acid catalyst at temperatures of 50 C. to 250 C. to obtain decahydroacenaphthene or an unsaturated decahydroacenaphthene such as octahydroacenaphthene or acenaphthene that can be easily hydrogenated to decahydroacenaphthene, in high yields. The cyclododecatriene utilized may be 98+ wt. percent material or may be a crude mixture containing approximately wt. percent cyclododecatriene along with other materials boiling closely with the distilled material, e.g. cyclooctadiene and vinyl cyclohexene.

According to the present process, reaction temperatures are 50 C. to 250 C., preferably C. to 225 C., e.g. C. and the reaction time required is in the range of 1 minute to 8 hours, preferably one-half hour to 5 hours, e.g. 2 hours. Pressures utilized in this liquid phase process are in general atmospheric pressure, although other pressures may, of course, be employed.

The acid catalysts which may be used in this invention may in general be any acid. Thus, these acids may be (1) the Lewis acids (also classed as Friedel-Crafts type catalysts used in conducting substitution reactions on a benzene type nucleus); (2) mineral acids such as H PO H 50 HCl or HNO (3) acid ion exchange resins such as sulfonated polystyrene resin, and (4) organic acids such as formic acid, trifluoroacetic acid, and toluene sulfonic acid. Examples of the Lewis acids are HF, A101 BF3, Zl'lClz, A1BI'3, FCC13, SbC1 P205, TeCl and SnCl The Lewis acids may be used alone or supported on inert supports such as alumina. Additionally, the strong acids from groups (1) and (2) above may be used in aqueous solution, dilute rather than concentrated acids being preferred. Preferred acids for carrying out the present isomerization process are concentrated phosphoric acid, phosphoric acid on kieselguhr, polyphosphoric acid, the Lewis acids above described, and sulfonated polystyrene resins. I

The amount of acid utilized should be in the range of from very small catalytic amounts (e.g. 1 wt. percent) to 1000 wt. percent, e.g. 300 wt. percent based on the cyclododecatriene supplied. The'hydrogenation step to convert unsaturated de'cahy droacenaphthenes to decahydroacenaphthene (after separation of high boiling polymer, e.g. low melting resin, and acid if necessary) is conducted utilizing conventional hydrogenation catalysts such as Raney nickel, nickel on kieselguhr, palladium on charcoal, platinum oxide, etc. Temperatures are preferably in the range of 125 C. to 300 C., more preferably 175 C. to 250 C., specifically 200 C. Pressures are preferably in the range of 1000 to 3500 lbs./in. more preferably 2000 to 3000 lbs./in. e.g. 2500 lbs./in.

Methods of carrying out the present invention in connection with preferred acids are described below.

Commercial polyphosphoric acid is utilized as the acid according to the general procedure described above. This acid is preferably a technical grade acid with an orthophosphoric acid equivalent of about 115%. The amount of polyphosphoric acid used should be in the range of catalytic amounts to 10 times the weight of cyclododecatriene supplied, preferably 2 times to 5 times, e.g. 3 times the weight of cyclododecatriene supplied. In this process in addition to decahydroacenaphthene small amounts of acenaphthene are obtained. This material may be removed by distillation to obtain both the desired pure decahydroacenaphthene and acenaphthane. Alternatively, in the preparation of a jet fuel a hydrogenation step may be employed on the entire reaction products after separation of polyphosphoric acid and distillation to separate high boiling polymer. Thus, the desired saturated stable jet fuel may be obtained directly in 75 to 85% yield.

Alternatively if pure acenaphthene in addition to decahydroacenaphthene is desired these materials may be separated directly in high purity from the organic layer from the polyphosphoric acid reaction by distillation. If acenaphthene is the main product desired, i.e. for use in conventional products such as intermediates for insecticides, fungicides and in the manufacture of plastics, the amount of this material obtained may be increased by utilizing temperatures in the range of 150 C. to 250 C., preferably 180 C. to 225 C., e.g. 200 C., and reaction times in the range of 1 hour to 5 hours, preferably 2 hours to 4 hours, e.g. 3 hours.

85 wt. percent aqueous orthophosphoric acid is used as the acid according to the general procedure described above to effect a rearrangement to octahydroacenaphthene. When this rearrangement step is followed by a hydrogenation step, as described above, the same decahydroacenaphthene product is obtained as when polyphosphoric acid is used as the agent causing rearrangement. The octahydroacenaphthene obtained by this process was identified by mass spectrometry the mass number of the parent peak being 162 for the octahydroacenaphthene and after it had been reduced with hydrogen the parent 'peak being 164. Further by means of gas chromotography it was shown that the reduced product was identical to the decahydroacenaphthene isolated by fractionation from the reaction products from polyphosphoric acid isomerization of cyclododecatriene. I

-A phosphoric acid on kieselguhr propylene polymerization (to .tetramer) catalyst having a 62-65 wt. percent P content is used in a slurry reaction as the acidaccording to the general procedure described above to effect a rearrangement to octahydroacenaphthene. The octahydroacenaphthene product was separated and was identified 4 by mass spectrometry and gas chromotography as previously described. A hydrogenation step as described above may also be used to give the same decahydroacenaphthene product. It should be noted. that essentially no acenaphthene is produced in the'reaction when 85 wt. percent orthophosphoric acid or the phoshporic acid on kieselguhr catalyst is used and that the lowest amounts of resin, e.g. less than 10 mol percent are obtained with the phosphoric acid on kieselguhr catalyst.

Alternatively to 'the'preparation of the improved jet fuel of this invention by butadiene trimerization, a decahydroacenaphthene prepared directly from a coal tar fraction containing acenaphthene may be utilized. This decahydroacenaphthene is prepared by hydrogenating the acenaphthene under conventional conditions. In general the same hydrogenation catalysts and conditions may be utilized as are described above in connection with the hydrogenation of the unsaturated decahydroacenaphthene product from the cyclododecatriene isomerization reactions.

The jet fuels of the present invention may also be used in a blend with typical petroleum distillate fractions, e.g. heavy naphthas, gasoline or kerosines. Thus, it is contemplated that 10 to 60 wt. percent of the decahydroacenaphthene material (based on the total blend) may be mixed with the distillate material. The jet fuel distillate which may be mixed with the present material are in general distillate fuels, naphthas and blends of these materials having an end point of the final jet fuel of at least 435 F. and preferably greater than 480 F. It will be understood, however, that the jet fuels which are employed according to this invention can contain certain other ingredients, such as alcohols or the like, provided the resulting fuel blend meets the specifications imposed upon jet fuels.

Typical jet fuels improved according to this invention include JP-3, i.e. a mixture of about 70% gasoline and 30% light distillate having a evaporated point of 470 F.; JP-4, a mixture of about 65% gasoline and 35% light distillate a fuel especially designed for high altitude performance; IP-S, an especially fractionated kerosene; high flash point-low freezing point kerosene, etc.

The present invention will be more clearly understood from a consideration of the following examples.

Example 1 Into a reaction flask equipped with stirrer, condenser, thermometer, and dropping funnel was placed 1798 g. of polyphosphoric acid. The acid was heated to 150 C. and 590 g. of cyclododecatriene was added slowly with stirring by means of the dropping funnel. After the addition was completed the reaction mixture was stirred and heated at 150 C. for 3 hours. At the end of this time the mixture was cooled to C. and then poured into a beaker which contained 2 kg. of ice. The organic layer was separated and the aqueous layer was extracted with successive portions of petroleum ether (900 ml. total). The petroleum ether extracts were combined with the organic layer and this solution was successively washed with water, 10% NaOH solution, water, and saturated NaCl solution. The petroleum ether solution was then dried over anhydrous MgSO, and the solvent was stripped off under vacuum.

The residue was then distilled under vacuum. The following reaction products were obtained:

In mole percent yield Decahydroacenaphthen Acenaphthene 10 Low-melting resin 25 The .acenaphthene product was conclusively identified by melting point and mixed-melting point determination with an authentic sample of acenaphthene. Also infrared scans of the product and authentic acenaphthene were identical. Decahydroacenaphthene was identified tentatively on the basis of mass spectrum analysis, infrared analysis, and gas chromatgraphic analysis of the product and comparison of these results with a sample of authentic decahydroacenaphthene from coal tar.

Example 2 Into a reaction :flask equipped with stirrer, condenser, thermometer, and dropping funnel was placed 248 g. of 85% orthophosphoric acid. The acid was heated to 148 C. with stirring and 65.6 g. of cyclodecatriene was added slowly. After the addition was completed, the reaction mixture was heated at 150 C. for 5 hours. The workup procedure was essentially the same as in Example 1. The material after workup was distilled under vacuum. The following reaction products were obtained:

In mole percent yield Octohydroacenaphthene 74 Low-melting resin 17.4

The octahydroacenaphthene was reduced with hydrogen over Raney nickel catalyst at 200 C. and 3000 lbs./ in. pressure. The product obtained was identified as decahydroacenaphthene by the same methods as in Example 1.

Example 3 Into a reaction flask equipped with condenser, stirrer, and thermometer was placed 325 g. of cyclododecatriene and 55.0 g. of a granulated commercial polymerization catalyst (commercial catalyst for polymerization of propylene to tetrapropylene. Consists of phosphoric acid commingled with kieselguhr. Catalyst has 6265% P content). The reaction mixture was heated to 150 C. .and stirred. The temperature was maintained at 150 C. for 3 hours. At the end of this time the mixture was cooled to about 90 C. and then the liquid product was separated from the solid catalyst by filtration. The liquid product was then distilled under vacuum. The following reaction products were obtained.

In mole percent yield Octahydroacenaphthene 83 Low-melting resin 9.2

The octahydroacenaphthene was reduced with hydrogen as in Example 2. The decahydroacenaphthene obtained was identified as before.

Example 4 The decahydroacenaphthene prepared as above described in Example 1 and separated by distillation was tested for jet fuel properties and the following data were obtained. Additionally data are presented comparing this material with a decahydroacenaphthene sample obtained by hydrogenating commercial acenaphthene separated from a coal tar fraction. Both of these materials are compared against the minimum requirements for an idealized jet fuel. The decahydroacenaphthene prepared in Examples 2 and 3 also tested similarly.

Decahydroacenaphthene prepared as above described in Example 1 and separated by distillation is burned in a jet engine as described in US. Patent 2,168,726.

Additionally fuels prepared as described in this invention are advantageously used for all types of jet propulsion whether of the rocket jet propulsion or jet engine type as will be described.

In jet propulsion the driving force of the body is produced by the forwardly directed forces of the reaction resulting from the rearward discharge from the body of a jet (a high speed stream) through an orifice. The forces responsible for the propulsion are exerted usually against the inside of the forward part of the body and are opposed to those expended by the rearward discharge of the jet.

A jet engine has one or more combustion chambers and one or more exhaust nozzles for the rearward discharge of a continuous or intermittent stream of fluid, usually heated air and exhaust gases. A jet plane may be powered by a jet engine that utilizes the surrounding air in the combustion of fuel or by a jet engine of the rocket type that carries its fuel and all the oxygen or other oxidizing agent necessary for combustion, and therefore functions independently of atmospheric oxygen.

There are three basic types of jet engines: ram jets, tunbo-jets and pulse jets. The working cycles of the ram jet and turbo-jet are essentially the same. The ram jet diifers from the turbo-jet in that compression in the former is obtained by the ramming effect of the oncoming air, while in the latter, air is forced into the combustion zone by means of a gas turbine. In the pulse jet engine, compression is obtained by the ramming effect of the oncoming air and the intermittent explosions of fuel which close the valves in the upstream portion of the combustion zone.

All of these jet engines operate in the same basic manner. Air enters the engine at the forward end and is heated by fuel burning in the combustion zone. The air and exhaust gases flow from the combustion zone through a rearwardly extending conduit at a velocity higher than the flying speed of the airplane. The thrust produced equals the gas mass flowing through the exhaust duct times its increase in speed, according to the law of momentum.

The foregoing description contains a limited number of embodiments of the present invention. It will be understood that this invention is not limited thereto since numerous variations are possible without departing from the scope of the following claims.

What is claimed is:

1. A process for the preparation of a material selected from the group consisting of decahydroacenaphthene, octahydroacenaphthene and acenaphthene and mixtures thereof which comprises reacting cyclododecatriene with an acid catalyst selected from the group consisting of HF, A101 B1 ZnCl AlBr FeCl SbCl Ticu, P 0 TeCl and SnCl acid ion exchange resins, organic acids, HCl, H PO H SO and HNO at temperatures in the range of 50 to 250 C. for 1 minute to 8 hours.

2. The process of claim 1 in which the acid catalyst is wt. percent aqueous orthophosphoric acid and the material prepared is octahydroacenaphthene.

3. The process of claim 1 in which the acid catalyst is a phosphoric acid on kieselguhr catalyst having a 6265 wt. percent P 0 content and in which the material prepared is octahydroacenaphthene.

4. A process for the preparation of a jet fuel which comprises isomerizing cyclododecatriene in the presence of an acid catalyst selected from the group consisting of I'IF, A1013, BF3, ZIlClz, AlBI'3, FeCl SbCl TiCl P205, TeCl and SnCl acid ion exchange resins, organic acids, HCl, H PO polyphosphoric acid, H SO and HNO at temperatures in the range of 50 to 250 C. for '1 minute to '8 hours, separating isomerized cyclododecatriene from the acid catalyst and high boiling resin polymer, and hydrogenating the isomerized cyclododecatriene in the 7 presence of a hydrogenation catalyst at temperatures in the range of 125 to 300 C. to obtain a saturated hydrocarbon jet fuel.

5. The process of claim 4 in which the acid catalyst is polyphosphoric acid.

6. The process of claim 4 in which the acid catalyst is 85% orthophosphoric acid.

7. The process of claim 4 in which the acid catalyst is phosphoric acid on kieselguhr catalyst having a 62-65 wt. percent P 0 content.

8. The new composition of matter octahydroacenaphthene having a molecular weight of 162.

8 References Cited UNITED STATES PATENTS 3,153,101 10/1964 Konecky et al. 3,070,638 12/1962 Voltz 260668 3,185,739 5/1965 Gray et al 260--666 DELBERT E. GANTZ, Primary Examiner.

C. E. SPRESSER, JR., Assistant Examiner.

U.S. Cl. X.R. 

